The present invention relates to a rotor configuration for an electric machine and, more particularly, to a rotor configuration including a magnetic shield member disposed between field winding modules and a rotor enclosure.
In a conventional electric machine such as a generator having a rotor and a stator, the rotor is provided with field windings that excite the generator while receiving a current from an exciting current source. The stator is provided with armature windings from which electrical power is output. Typical rotor construction requires a field winding be assembled bar by bar, into radial slots milled into a rotor forging. Containment of the rotor field windings is typically achieved using rotor wedges, rotor teeth and retaining rings.
As rotor wedges, conventional generator fields use axial slotted forgings to wedge in the copper field winding turn by turn. As a result, the significant mass of copper is strongly coupled with the rotor shaft as an integral entity. The end winding is then typically enclosed by two thick metallic retaining rings, which are attached to the rotor body via shrink fit. The configuration provides strong support for huge centrifugal forces from field windings under high rotation speed and axial stiffness for steady rotor dynamics behavior.
The current configuration, however, defines the process by which the windings are assembled and how the rotor is machined. The rotor size, especially the diameter, is limited by the material strength of the shaft and retaining rings.
A simplified rotor enclosure is described in U.S. Pat. No. 6,495,942. This construction replaces conventional containment components with a simplified enclosure.